The six essays deal comprehensively with various themes in Wittgenstein''s philosophy: the relationship between his mathematics and his philosophy of mind; his conception of grammar and rules of grammar; the relation between a rule and what accords with a rule; the characterization of rule-following as mastery of a technique manifest in practice; his notion of a form of life, and of agreement in definitions and judgements; a comprehensive investigation into his account of logical and mathematical necessity and other topics.